Ok, I have some serious concerns about venting.

[bluegiller]

Sorry I should have started my own new post but I posted in this thread instead. ( http://forum.caswellplating.com/show...?t=3916&page=3 )

The oven is 6x4x3 and is constructed of steel studs and durock.

Heat is supplied by a 175k-350k LP Forced air unit.

Now to my question('s), Do I need a vent of some sort on this unit?

I wanted to use Electric elements but I know nothing about electrical wiring, amp, voltage etc.

I may use "loosely knitted" rope for a really snug seal, is fiberglass an acceptable form of material? http://www.mcmaster.com , rope seal , 8818K45

I'm stressing because, after all it is PROPANE..!!

ANY info would be great, Thanks a lot.

[bluegiller]

Re: Ok, I have some serious concerns about venting.

almost 40 views and no one willing to jump in?

Im in the middle of another test run with a 2 foot extension tube and i put 2 pieces of expanded metal near the inlet inside of the oven to deflect some air but it still seems to powerfull.

[pickleboy]

Re: Ok, I have some serious concerns about venting.

almost 40 views and no one willing to jump in?

Im in the middle of another test run with a 2 foot extension tube and i put 2 pieces of expanded metal near the inlet inside of the oven to deflect some air but it still seems to powerfull.

i will try to help but since i have not built my own oven i may be of little help. as for the vent yes you should have some sort of vent. i would suggest that you make it a damper type of vent. this will help you regulate the temp without having to start and stop the heater. as for the air flow it may have to have some sort of solid baffle system that will difuse the air so as to not blow the powder off the part.
"I'm stressing because, after all it is PROPANE"
as for the worries on propane i think it should be safe as long as you are very careful with the bottle placement. propane generally burns about 90-98% clean, so fume problems should be minimal. hope this helps some bro.

[bluegiller]

Re: Ok, I have some serious concerns about venting.

Thanks a lot.

I'm not even getting close!! I need another 100 degrees and it just isn't happening, this is so aggrevating.

I believe there is to much airflow kicking back to the heater and the flame is going over the back side of the heater and that is when it cuts/turns off.

I have no clue what a solid baffle or a damper is but I will goggle it and hope to find some info out.

I read in other threads where people talked about the dampers but Im just not familar with them.

I'm so frustrated its unreal..

I will go to electric if I cant get this propane to work, I just really needed to get the frame done before christmas.

Thanks for the reply

[pickleboy]

Re: Ok, I have some serious concerns about venting.

damper would be a tube with a disc in it that will open to full flow or close all the way across the tube to close it. like a butterfly valve if you are familar with them. or similar to a fireplace chimney flue. as for solid baffles you may need to build some sort of plates alternating diagonoly from left to right then right to left in kind of a stairstep stagger. this will slow down the flow of air to the box but should stop most of the backpressure to the heater. if all else fails cut a small v notch in the end of the extension pipe from the heater to the box. this will allow some of the airflow to escape and also relieve backpressure. if i could draw on here i would since my explaining is not the best. if you are getting backpressure on the discharge end of that heater it will cause an overtemp and shutdown. if you need help shoot me a pm and i will give you my phone # so you can call.

[sswee]

Re: Ok, I have some serious concerns about venting.

The air that the heater puts out is pressurizing you oven and backpressuring into the heater causing the thermal overheat switch to shut down the heater. That type of heater has the switch as a safety feature to keep from burning the heater up.
A damper in that respect is going to be a hole probably equal in size to the inlet but located in the top of the opposite side and will have a piece that can be rotated to cover the vent hole in any amount desired. Dampers are commonly used on BBQ pit stacks as a plate that rotates over the top of the smoke stack or fireplaces as a disc inside the smoke pipe that can be rotated to restrict or dampen the heat flow out of the pipe.

I understand your hesitance in delving into the electrical way if your not familiar with it but due to the safety issues, you aren't going to get the assistance as you will going electric. I hope you understand. SS

[pickleboy]

Re: Ok, I have some serious concerns about venting.

but due to the safety issues, you aren't going to get the assistance as you will going electric. I hope you understand. SS

sswee is right on this, gas heat source is not the safest way to go. it has been done by quite a few here and elsewhere. the only way gas heat is truly safe is if in a sealed burner box and air is forced around to draw the heat off said box, like a heat exchanger in your house furnace. also keep in mind that gas heat (natural or propane) being combustion in nature will produce water vapor as a byproduct of the burn. that said if your heater blows right in your oven box it can contaminate the pc job as it cures. not a fact it will happen but could.

[bluegiller]

Re: Ok, I have some serious concerns about venting.

Thanks guys, Well I just done removing 2 of the 4 blades on the heater fan to try and slow the air flow, needless to say the backpressure is still there...

The damper idea must work but just seems like it would let to much heat out
(trust me I understand you can/do meter the flow out.)

As far as the homemade baffles your speaking of I'm a bit lost so will take you up on you phone call offer, pm on its way.

Thanks fellas.

[hvac36]

Re: Ok, I have some serious concerns about venting.

Thanks guys, Well I just done removing 2 of the 4 blades on the heater fan to try and slow the air flow, needless to say the backpressure is still there...

The damper idea must work but just seems like it would let to much heat out
(trust me I understand you can/do meter the flow out.)

As far as the homemade baffles your speaking of I'm a bit lost so will take you up on you phone call offer, pm on its way.

Thanks fellas.

Ok here is the deal, unless you get the flame out of the Oven and place it in a SEALED heat exchanger that oven is UNSAFE!! Open Flame and Blowing Powder DO NOT MIX!!! Well they do but the mix is NOT a good MIX.
Either buy a Gas oven from a company that makes them for this use or Build and electric oven please..
Need help wiring it I will be more then happy to talk you thru it or draw you and image or snap a Image of mine...
Lets be safe folks...

Jim S....

[bluegiller]

Re: Ok, I have some serious concerns about venting.

Ok here is the deal, unless you get the flame out of the Oven and place it in a SEALED heat exchanger that oven is UNSAFE!! Open Flame and Blowing Powder DO NOT MIX!!! Well they do but the mix is NOT a good MIX.
Either buy a Gas oven from a company that makes them for this use or Build and electric oven please..
Need help wiring it I will be more then happy to talk you thru it or draw you and image or snap a Image of mine...
Lets be safe folks...

Jim S....

Thanks for suggestion, It certainly looks like I'll be going electric with this oven.

I should be able to get a pretty penny for this heater that should cover any expense all the electronics will cost.

What about Radiant heaters??

Thanks again

[tinbender722]

Re: Ok, I have some serious concerns about venting.

Bluegiller,

Is this a torpedo type heater? I have been running a 150,000 btu one in a 6'x'4'x6' self built oven for a year with no problem. It will get to 520 degrees.
I also have a factory made 8'x8'x15' oven with a 1,000,000 btu propane burner. The oven needs to be vented to work right. Cut a 8" - 10" diameter hole at the top in the side of the oven and vent to outside. Or, change over to electric and send me a picture of your burner and the price - I am ready to build another oven and may be real interested in buying the burner.

Leo

[bluegiller]

Re: Ok, I have some serious concerns about venting.

Well after talking to pickle he pointed out that perhaps the propane bottle was frosting up, then the propane would not burn as efficent.
After another test run last night with the top door cracked a 1/4 inch for venting, the bottle did fost over and the temputure in the oven droped a lot when this happened. It came up to 275 pretty fast and then when the frost hit the propane tank it drop almost 75 degrees. (210)

I hop you don't mind tin man but I going to give you a call at the shop and try to figure out the proper venting system.

Here is a couple pics of the oven again. (I have a 2 foot extension tube now on the end of the heater.)

[jjucius]

Re: Ok, I have some serious concerns about venting.

My oven is 3' x 5' x 7' and i'm using a 375,000 btu heater i have a 40 pound tank but i am getting atleast 1 100 pound tank soon. on a heater that size you should use 1 or 2 tanks so the pressure keeps up. i have to put in anouther vent because mine heats up to 400 in 5 minutes 10 minutes it went up to 530 right now if i open the door half way it will sit at 410 i have the heater ducted in to the back and a 8 inch vent with a stove damper on top towards the front. i have no problem with powder blowing off but i need to put some type of deflector in the oven because it gets too hot where the heat comes in and tends to burn the powder if parts are hanging close to it. i will try to get some pics up soon.
Joe